Antibiotic therapy completion for injection drug use-associated infective endocarditis at a center with routine addiction medicine consultation: a retrospective cohort study | BMC Infectious Diseases

Ultimately, 65.1% of our cohort’s survivors completed antibiotic therapy, 87.2% were seen by addiction medicine specialists and 89.4% received MOUD. This rate of MOUD initiation differs greatly from the initiation rate of 5.7% reported in a nationwide study of IDU-IE patients [8]. Antibiotic therapy completion in IDU-IE has not been studied extensively; one study of 26 patients reported a completion rate of 92.3% [9]. In a study of patients hospitalized with infectious complications of IDU including but not limited to IDU-IE, 52.0% completed antibiotic therapy, and 30.4% received addiction medicine consultation [5]. Notably, 38.4% of patients in that study received MOUD, whereas 48.9% of patients in our study received it for their entire hospitalization. Thus, a sizeable fraction of patients in both cohorts did not complete antibiotic therapy despite relatively higher use of SUD-oriented interventions at our facility.

In the cohort of Marks et al. [5], 113 IDU-IE patients were included. An overall 90-day readmission rate of 36.3% was found; among those with and without addiction medicine evaluation, this rate was 28.6% and 54.5%, respectively (LR Marks, personal communication, June 5, 2020). In our study, a longer follow-up period was examined, and 88.4% of patients were re-hospitalized at least once. Thus, at our center with its widespread utilization of SUD-directed interventions, readmissions were common. MOUD may be just one critical component of improving outcomes among this population; others have called for broader awareness of social determinants of health, stating that medical interventions represent just one aspect in optimizing the care of this vulnerable patient population [10].

Transitions of care are a key consideration in evaluating the outcomes observed in our study, since most survivors in our cohort were discharged to subacute facilities. Federal policy, specifically Title 21 of the Code of Federal Regulations, complicates patients’ receipt of MOUD at these facilities, preventing continuation of MOUD started in the inpatient setting unless the patient is already enrolled in an OUD treatment program [11]. While facilities were expected to continue appropriate therapies after discharge, we were unable to independently verify continuation of MOUD after discharge. Strategies to improve outcomes among those transitioning to a non-facility setting have also been studied. In one randomized trial of patients with an IDU-related infection, patients in the experimental arm underwent frequent outpatient visits following an inpatient stay rather than remaining hospitalized for antibiotic therapy alone; all completed antibiotic therapy [12], suggesting careful planning after discharge can improve antibiotic therapy completion. SUD-specific care management teams have been proposed [13]and may provide key support while patients transition to the outpatient setting.

The major limitation of our study is its sample size, which limited the ability to perform analytical statistics beyond descriptive calculations. Although not all patients were seen by the addiction medicine service, dichotomizing the sample by that factor created subgroups that were themselves too small for an analytic approach. Similarly, the absence of a control group also prevented us from taking an analytical approach. The boundaries of the eligibility window, which determined the study size, were chosen to allow for exclusive use of ICD-10 billing codes while leaving sufficient time for 12 months of follow up. ICD-10 codes were only used to capture infection-related diagnoses , and not to identify SUDs, for which they are unreliable [14, 15]. In addition, the study eligibility window accounted for the availability of addiction medicine consultation, and allowed study results to reflect contemporary issues in the treatment of IDU-IE. This is particularly pertinent because fentanyl increasingly replaced heroin to become the dominant opioid in our region over the period of the study [16]. Other key limitations were the inability to assess engagement in SUD-specific care and receipt of MOUD after hospital discharge. While the availability of post-discharge MOUD receipt data would have added greatly to the study’s impact, these data were not available as described above. Additionally, follow up data were not available for two individuals. A final limitation of our study is that it was performed at a single institution that largely cares for underserved and low-income patients, and so its generalizability is limited.

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